/**
 * #      730
 * 名称   统计不同回文子序列
 * 链接   https://leetcode-cn.com/problems/count-different-palindromic-subsequences
 * 题解   [39](https://leetcode-cn.com/problems/count-different-palindromic-subsequences/solution)
 * 通过率 47.7%
 * 难道   困难
 */

